A so-called land grid array (LGA) semiconductor package has a surface on one side on which pads are arranged in a grid pattern. The pads are connected to, for example, a motherboard. For example, the pads are connected by using an LGA socket having a resilient connection terminal(s) penetrating through a resin substrate. Various modifications are made to the LGA semiconductor package, so that high frequency signals of the LGA semiconductor package are maintained having satisfactory transmission characteristics. One example is described below.
FIG. 1 is a bottom view illustrating an example of a pad arrangement of a semiconductor package 200 according to a related art example. The semiconductor package 200 is a so-called LGA package having a bottom surface on which pads are arranged in a grid pattern. Pads 210G are electrically connected to a reference potential of the semiconductor package 200. Pads 210S are used for a single end signal. The pads 210G and the pads 2105 are alternately arranged. For the sake of convenience, the pads 210G are illustrated with a matte surface in FIG. 1.
FIG. 2 is a bottom view illustrating another example of a pad arrangement of a semiconductor package 300 according to a related art example. The semiconductor package 300 is a so-called LGA package having a bottom surface on which pads are arranged in a grid pattern. Pads 310G are electrically connected to a reference potential of the semiconductor package 300. Two pads 310G are consecutively arranged on the semiconductor package 300. Pad 310S are used for a differential end signal. Two pads 3105 are consecutively arranged on the semiconductor package 300. Two pads 310S are consecutively arranged for increasing the bond among signals transmitted from each of the pads 310S and cancelling out noise components among the pads 310S. Two of the pads 310G and two of the pads 310S are alternately arranged. For the sake of convenience, the pads 310G are illustrated with a matte surface in FIG. 2.
On the other hand, it is common for connection terminals of the LGA socket to be separately exposed to the atmosphere. Therefore, unless the connection terminal of the LGA is shielded at the GND, problems such as mismatch of characteristic impedance may occur and adversely affect transmission characteristics of high frequency signals. Thus, it is preferable to shield each of the connection terminals of the LGA socket at the GND, so that high frequency signals can maintain satisfactory transmission characteristics in correspondence with the pad arrangements illustrated in FIGS. 1 and 2.
[Patent Document 1]
Japanese Laid-Open Patent Publication No. 2010-277829
Japanese Laid-Open Patent Publication No. 09-017535
The width of a data bus and the number of channels are increasing due to the increasing speed of semiconductor packages whereas the pitch between connection terminals of the LGA is becoming narrower due to size reduction of the semiconductor package. However, it is difficult to reduce the pitch between connection terminals shielded at the ground.